1. Field of the Invention
The present invention relates generally to heat exchangers and, more specifically, to a heat exchanger and method of assembly for an automotive vehicle.
2. Description of the Related Art
It is known to provide automotive vehicles with heat exchangers such as condensers, evaporators, heater cores and coolers. These heat exchangers are alternating rows of tubes or plates with convoluted fins made of a metal material such as aluminum or an aluminum alloy. Many of these heat exchangers have turbulators disposed within the tubes that require internal brazing. Previously, the tubes and turbulators have been brazed in a vacuum furnace. Recently, a process known as xe2x80x9ccontrolled atmosphere (CAB)xe2x80x9d furnace brazing has been used with non-corrosive fluxes. CAB furnace brazing has been preferred over vacuum furnace brazing due to improved production yields, lower furnace maintenance requirements and greater braze process robustness.
It is also known that the CAB furnace brazing currently used to manufacture aluminum heat exchangers requires the use of fluxing agents, either chloride based or fluoride based. The use of fluxing agents with conventional aluminum heat exchangers promotes the dissociation and disruption of the native aluminum oxide and magnesium oxide layers present on the surface of the aluminum heat exchanger to promote wetting of the molten clad layer between mating components.
Although CAB furnace brazing has worked well, it suffers from the disadvantage that the internal tube surfaces and the turbulator of the heat exchanger require individual fluxing before assembly and an overall fluxing of the completed assembly before brazing. Also, CAB furnace brazing suffers from the disadvantage that flux residues can block internal tube passages. Further, CAB furnace brazing suffers from the disadvantage that the individual fluxing of the components of the heat exchanger is costly and time consuming.
It is further known that the tubes of the heat exchanger are generally welded along a seam located at an end radius of the tubes. During the welding process, an external cladding on the tube is typically disrupted and missing from an external surface of the tube before brazing. The absence of cladding on the external surface of the tube can lead to lower strength and durability of the tube along and surrounding the weld seam, which is undesired.
Accordingly, the present invention is a heat exchanger assembly for an automotive vehicle including at least one tube having an internal surface and an external surface and a composition cladding having at least magnesium applied to the internal surface and external surface of the tube.
Also, the present invention is a method of assembly of a heat exchanger for an automotive vehicle including the steps of providing at least one tube having an internal surface and an external surface. The method includes the steps of applying a composition cladding having at least magnesium to the internal surface and external surface of the tube.
One advantage of the present invention is that a heat exchanger assembly is provided for an automotive vehicle that has a composition cladding having at least elemental magnesium that allows for fluxless internal brazing of the heat exchanger assembly without the application of a fluxing agent to promote oxide layer breakdown. Another advantage of the present invention is that the heat exchanger assembly has an internal row of dimples to act as a turbulator and improve tube strength for durability. Yet another advantage of the present invention is that the heat exchanger assembly eliminates the use of flux and is less expensive and less time consuming to manufacture. A further advantage of the present invention is that a method of assembly of the heat exchanger is provided which eliminates flux residues that can block internal tube passages. Yet a further advantage of the present invention is that the heat exchanger assembly has a tube with a double side composition cladding in which the internal composition cladding can be used to reinforce the weld seam region of the tube. Still a further advantage of the present invention is that the internal composition cladding reinforces the weld seam to increase the strength and pressure cycling durability of the tube.
Other features and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in conjunction with the accompanying drawings.